Passive needle guard for syringes

Abstract

A passive needle guard includes a body having proximal and distal ends and a cavity therein for receiving a medicine cartridge, and a shield slidable on the body between retracted and extended positions for exposing and covering, respectively, a needle extending from the body, the shield being biased towards the extended position. Deflectable latch members extend from the shield that include catches for engaging catches on the body for holding the shield in the retracted position. A syringe is inserted into the needle guard, and a needle of the syringe inserted into a patient. A plunger of the syringe is depressed to inject medication and to deflect the latch members to disengage the catches and release the shield, whereupon the shield automatically advances to the extended position. In the extended position, cooperating detents on the shield and body engage one another, thereby preventing subsequent retraction of the shield.

What is claimed is:  
     
       1. A passive needle guard, comprising: 
       a body having open proximal and distal ends an a cavity therein for receiving a medicine cartridge through the open proximal end, the medicine cartridge comprising one of a syringe, ampoule or vial for containing medicine;  
       a shield having proximal and distal ends, the shield being slidably attached to the body and slidable between a retracted position for exposing a needle extending from the distal end of the body, and an extended position for substantially covering the needle, the shield being biased to slide towards the extended position;  
       cooperating catches on the body and shield for engaging one another to hold the shield in the retracted position; and  
       a latch member extending proximally from the proximal end of one of the shield and the body, the latch member being deflectable for disengaging the cooperating catches upon depression of a plunger coupled to the medicine cartridge, whereby the shield may be automatically advanced to the extended position.  
     
     
       2. The passive needle guard of  claim 1 , further comprising a spring mechanism coupled to the body and the shield for biasing the shield towards the extended position. 
     
     
       3. The passive needle guard of  claim 2 , wherein the spring mechanism comprises a compression spring disposed between the body and the shield. 
     
     
       4. The passive needle guard of  claim 2 , wherein the spring mechanism comprises a spring concentrically disposed within the shield. 
     
     
       5. The passive needle guard of  claim 1 , further comprising cooperating detents on the shield and the body, the cooperating detents configured for engaging one another when the shield is disposed in the extended position to prevent retraction of the shield. 
     
     
       6. The passive needle guard of  claim 5 , wherein the cooperating detents comprise a detent on the shield and a detent pocket on the body, the detent and detent pocket having substantially blunt proximal edges for preventing proximal movement of the shield from the extended position. 
     
     
       7. The passive needle guard of  claim 1 , wherein the cooperating catches comprise a first catch on the latch member and a second catch on the body, the latch member being resiliently deflectable radially for disengaging the first catch from the second catch. 
     
     
       8. The passive needle guard of  claim 7 , wherein the latch member comprises an elongate finger extending proximally from the shield and having a proximal tip that is engageable by the plunger to compress and deflect the latch member radially outwardly. 
     
     
       9. The passive needle guard of  claim 1 , further comprising a locking mechanism on the proximal end of the body for substantially securing the medicine cartridge in the cavity. 
     
     
       10. The passive needle guard of  claim 9 , wherein the locking mechanism comprises a plurality of locking detents on a finger grip on the proximal end of the body. 
     
     
       11. The passive needle guard of  claim 1 , further comprising a finger grip on the proximal end of the body, the finger grip including a pair of axial flanges extending distally therefrom, the axial flanges being spaced away from the body to accommodate the shield sliding therebetween. 
     
     
       12. A method as in  claim 1  wherein the medicine cartridge is a prefilled syringe. 
     
     
       13. A method as in  claim 1  wherein the medicine cartridge is a unit dose syringe. 
     
     
       14. A passive needle guard, comprising: 
       a body having proximal and distal ends and a cavity therein for receiving a medicine cartridge;  
       a shield having proximal and distal ends, the shield being slidably attached to the body and slidable between a retracted position for exposing a needle extending from the distal end of the body, and an extended position for substantially covering the needle; and  
       a spring mechanism coupled to the body and the shield for biasing the shield towards the extended position, the spring mechanism having a nonlinear spring rate such that the spring rate when the shield is in the retracted position is substantially less than the spring rate as the shield approaches the extended position.  
     
     
       15. The passive needle guard of  claim 14 , further comprising: 
       cooperating catches on the body and shield for engaging one another to hold the shield in the retracted position; and  
       a latch member for disengaging the catches, whereupon the shield may automatically advance to the extended position.  
     
     
       16. The passive needle guard of  claim 15 , wherein the latch member comprises a finger extending proximally from the proximal end of one of the shield and the body, the finger being deflectable for disengaging the cooperating catches upon depression of a plunger coupled to the medicine cartridge. 
     
     
       17. The passive needle guard of  claim 14 , wherein the spring mechanism comprises a compression spring disposed between the shield and the body. 
     
     
       18. A method as in  claim 14  wherein the medicine cartridge is a prefilled syringe. 
     
     
       19. A method as in  claim 14  wherein the medicine cartridge is a unit dose syringe. 
     
     
       20. A method for assembling a passive needle guard, comprising: 
       providing a body having a cavity therein for receiving a medicine cartridge, the medicine cartridge comprising one of a syringe, ampoule or vial for containing medicine;  
       directing a proximal end of a tubular shield over a distal end of the body;  
       directing the shield towards a proximal end of the body from an extended position wherein a distal end of the shield extends beyond the distal end of the body towards a retracted position wherein the distal end of the shield is substantially coextensive with the distal end of the body;  
       coupling a spring between the body and the shield, the spring biasing the shield to advance towards the extended position;  
       deflecting a latch member on one of the body and shield to prevent contact between mating catches on the body and shield as the shield is directed to the retracted position; and  
       releasing the latch member once the shield has attained the retracted position to engage the mating catches and substantially secure the shield in the retracted position.  
     
     
       21. A method for performing an injection using a passive needle guard including a body having a medicine cartridge therein and a shield slidably attached to the body, the medicine cartridge comprising one of a syringe, ampoule or vial for containing medicine and, the shield being biased to advance to an extended position for covering a needle extending from the passive needle guard and retained by cooperating catches on the body and shield in a retracted position wherein the needle is exposed, the method comprising: 
       inserting the needle into a patient with the shield retained in the retracted position;  
       depressing a plunger communicating with the medicine cartridge to inject medication into the patient until the plunger engages a latch member extending from the passive needle guard; and  
       depressing the plunger further to deflect the latch member radially to disengage the cooperating catches, and release the shield, whereby the shield may automatically advance towards the extended position.  
     
     
       22. The method of  claim 21 , further comprising withdrawing the needle from the patient, the released shield automatically advancing fully to the extended position covering the needle. 
     
     
       23. The method of  claim 21 , wherein cooperating detents on the shield and body engage one another when the shield is advanced to the extended position, thereby preventing subsequent proximal movement of the shield. 
     
     
       24. The method of  claim 21 , wherein the latch member comprises a finger extending from the shield towards the plunger, the finger being compressed and thereby deflected radially outward when the plunger is depressed to disengage a catch thereon from a mating catch on the body. 
     
     
       25. The method of  claim 24 , wherein the plunger includes a radial portion for engaging a proximal tip of the finger as the plunger is depressed, the finger being compressed and thereby deflected radially outward thereby. 
     
     
       26. A passive needle guard, comprising: 
       a body having proximal and distal ends and a cavity therein a medicine cartridge in the cavity;  
       a shield having proximal and distal ends, the shield being slidably attached to the body and slidable between a retracted position for exposing a needle extending from the distal end of the body, and an extended position for substantially covering the needle, the shield being biased to slide towards the extended position;  
       cooperating catches on the body and shield for engaging one another to hold the shield in the retracted position; and  
       a latch member extending proximally from the proximal end of one of the shield and the body, the latch member being deflectable for disengaging the cooperating catches upon depression of a plunger coupled to the medicine cartridge, whereby the shield may be automatically advanced to the extended position.  
     
     
       27. The passive needle guard of  claim 26 , wherein the medicine cartridge includes a plunger slidably received in its proximal end, the plunger including a radial portion for engaging the latch member when the plunger is depressed distally into the medicine cartridge to disengage the cooperating catches. 
     
     
       28. The passive needle guard of  claim 27 , wherein the radial portion is provided on an intermediate region of the plunger. 
     
     
       29. The passive needle guard of  claim 27 , wherein the radial portion comprises a thumb pad on a proximal end of the plunger. 
     
     
       30. The passive needle guard of  claim 27 , wherein the latch member extends from the proximal end of the body a predetermined distance and the radial portion is provided on a predetermined location of the plunger, such that the cooperating catches are disengaged before complete depression of the plunger. 
     
     
       31. A method for assembling a passive needle guard, comprising: 
       providing a body having a cavity therein with a medicine cartridge in the cavity;  
       directing a proximal end of a tubular shield over a distal end of the body;  
       directing the shield towards a proximal end of the body from an extended position wherein a distal end of the shield extends beyond the distal end of the body towards a retracted position wherein the distal end of the shield is substantially coextensive with the distal end of the body;  
       coupling a spring between the body and the shield, the spring biasing the shield to advance towards the extended position;  
       deflecting a latch member on one of the body and shield to prevent contact between mating catches on the body and shield as the shield is directed to the retracted position; and  
       releasing the latch member once the shield has attained the retracted position to engage the mating catches and substantially secure the shield in the retracted position.  
     
     
       32. The method of  claim 31 , wherein the medicine cartridge is inserted axially into a proximal end of the body. 
     
     
       33. The method of  claim 32 , wherein a locking mechanism on the proximal end of the body engages the medicine cartridge when it is fully inserted into the cavity to substantially permanently encapsulate the medicine cartridge therein. 
     
     
       34. The method of  claim 32 , wherein the latch member is deflected radially outwardly as the medicine cartridge is inserted into the body while retaining the shield in the retracted position.